1. Field of the Invention
This invention relates to a fine working method of a crystalline material. Particularly, the present invention relates to a fine working method of a crystalline material which performs etching working by use of a focused ion beam as a part of the working steps.
2. Related Background Art
In the prior art, as the fine working method by use of etching of a crystalline material such as bulk or thin film single crystalline materials, etc., there have been generally employed the method in which a resist, etc. is coated on its worked surface, a desired resist pattern is formed by lithography and then the portion without such resist pattern is removed chemically or physically.
However, in the above working method, for fine etching working with a line width of 1 micron or less, etching with high precision can be effected with difficulty, with resolution of the resist and expansion of the working region during etching presenting obstacles.
Also, according to the etching method as described above, working of a crystalline material into a cross-sectional shape having a region of reverse tapered shape or hollow shape could be done with extreme difficulty for the following reasons.
In the prior art, when working into a reverse tapered shape or a tunnel shape, anisotropic working has been practiced. Such anisotropic working utilizes the fact that etching speed is remarkably different depending on the crystal orientation. Accordingly, the crystal orientation of a crystalline material must be matched previously to a shape desired to be worked, and therefore this method could be applied only to a single crystalline material with limited orientation. Additionally, it could not be applied to those with different crystal orientations within the same plane such as a polycrystalline material. Further, when working in shape of a tunnel is to be performed, a bore must be opened at the side surface of the sample and the bore must be excavated by etching.
On the other hand, other than the fine working method according to lithography by use of a resist, there is also the method by use of focused ion beam. For example, J. Vac. Sci. Tehnol. B, Vol. 6, No. 3, p. 1014-1017, May/Jun 1988 "Fabrication of one-dimensional GaAs wires by focused ion beam implantation" shows fine working with a line width of 1 micron or less. Also, here is shown an example, in which etching is effected by use of HC1 after injection of focused ion beam injection of Si ions onto a GaAs substrate. However, also nothing is shown here about application to a complicated working such as hollow shape onto a crystalline material.